parser fix

Author: catamorphism

icu4c/source/i18n/messageformat2_parser.cpp

@@ -2006,6 +2006,9 @@ void Parser::parseSelectors(UErrorCode& status) {
             break;                                 \
         }                                          \
 
+    // Parse required whitespace before first variant
+    parseRequiredWhitespace(status);
+
     // Parse variants
     // matcher = match-statement s variant *(o variant)